Methods and compositions for reducing chlorine demand, decreasing disinfection by-products and controlling deposits in drinking water distribution systems

ABSTRACT

Methods and compositions for improving water quality by reducing chlorine demand, decreasing disinfection by-products and controlling deposits in drinking water distribution systems include adding low concentrations of supplemental oxidants, for example, RE-Ox® to the systems.

This application is a continuation of U.S. patent application Ser. No.11/973,872 filed on Oct. 9, 2007, now abandoned and further claimspriority to U.S. Provisional Patent Application No. 60/828,879 filed onOct. 10, 2006. Each of the foregoing applications is hereby incorporatedby reference herein, for all purposes.

BACKGROUND

Water contains organic matter, dissolved solids and minerals thatdeposit scale and film on surfaces in drinking water distribution pipesand equipment. Quality and flow of drinking water is deleteriouslyaffected by these scales and films. In addition, many cleaning andsanitizing agents leave film residues. Use of the methods andcompositions described herein control these deposits.

A variable matrix of organic and inorganic deposits accumulates on theinterior surfaces of all drinking water distribution piping systems.Control of such deposits is the key to improved water quality, lowermaintenance costs and efficient use of disinfectants. Organic-ladendeposits of this kind are a significant source of increased chlorinedemand and they can produce precursors of trihalomethanes and haloaceticacids disinfection byproducts. Variously called biofilms, scale ortuberculations, many deposits in drinking water systems have been shownto harbor and protect pathogenic or otherwise troublesome bacteria,viruses, algae and algal toxins, fungi, protozoa and invertebrates. Manytypes of microorganisms can proliferate in such deposits, and theirtoxic by-products can become problematic. Regardless of the level ofresidual disinfectant, microorganisms within these harborage depositshave been proven to periodically slough off and re-entrain into theflowing water, thereby contaminating other systems and exposingsusceptible consumers to biological hazards from drinking water systemsin the buildings they occupy.

Nearly everyone is familiar with “scale” such as occurs in a tea potused with hard water. The white precipitate is calcium carbonate and itdeposits onto the surface of the pot because the solubility of the saltis inversely related to temperature: as the temperature increases, thesalt precipitates. But in drinking water systems, the scaling process ismore complex and the water is not boiled (boiling water has a verydestructive effect on organic compounds in water). Deposits in drinkingwater systems never include just calcium carbonate (or other inorganicsubstances). This is because organic materials in the water are prone toadhering to surfaces. Native organic compounds from bulk drinking wateraccumulate onto surfaces because adsorption is thermodynamicallyfavored. Consequently, the deposits on surfaces in drinking waterdistribution systems include organic compounds and inorganic compoundssuch as “scale”. These organic materials give the depositcharacteristics which are much different than those scale deposits seenon the surface of a tea pot, for example.

SUMMARY

Methods for improving water quality by reducing chlorine demand,decreasing disinfection by-products and controlling deposits in drinkingwater distribution systems, include the steps of:

(a) determining the concentration of supplemental oxidants needed toimprove water quality; and

(b) producing the needed concentration in drinking water distributionsystems by adding the supplemental oxidants at a point afterdisinfectants are added to the system. If oxidants were used asdisinfectants, it would be at a much higher concentration than thesupplemental oxidants as disclosed herein.

A suitable oxidant is RE-Ox® which includes sodium hypochlorite.

RE-Ox® is prepared by:

(a) using high grade evaporated salt in a single pass brine system.

(b) electrolyzing the brine to form chlorine gas and sodium hydroxideusing the apparatus of FIGS. 1-8; sodium ions, hypochlorite ions,hypochlorous acid and chloride ions may result;

(c) bleeding a small amount of sodium hydroxide; and

(d) forming sodium hypochlorite in the form of RE-Ox®.

RE-Ox® Deposition Control Chemical is a unique oxidizing solution. Thesolution is made of hypochlorous acid as well as other oxidizingcompounds that have not been identified. The sum of all these oxidizingcomponents results in a solution that very effectively disrupts theorganic-laden deposits that accumulate in potable water distributionsystems. The concentration of RE-Ox® described herein for drinking waterdistribution systems is far below that for which RE-Ox® would act as anantimicrobial agent. That is to say, the chemical is not acting as adisinfectant or biocide at these low concentrations but rather, it isacting to disrupt the deposits on surfaces in distribution systems.Furthermore, supplemental oxidants comprising sodium hypochlorite, e.g.,RE-Ox®, are introduced into the water supply after disinfectants areadded to the system.

RE-Ox® is applied at very low concentrations, below concentrations thatwould have any antimicrobial effect. At these very low levels, oxidantsin the RE-Ox® solution, including hypochlorous acid, oxidize certaincomponents of deposits in drinking water systems. These deposits includeorganic and inorganic compounds. The oxidizable components of thedeposits are affected by the oxidants in RE-Ox®. In particular, theorganic components of these deposits act like “glue” to hold thedeposits together on surfaces.

RE-Ox® has been quantitatively shown in real world trials tosuccessfully control deposits in drinking water systems. The use of verylow concentrations such as 1-100 ppb of RE-Ox® in municipal drinkingwater systems reduces chlorine demand, decreases disinfectionby-products (THMs and HAA5s), and controls deposits.

Surprising deposit control effects have been observed in the followingconcentration ranges of RE-Ox® (product): 1 gallon product dosed to10,000 gallons of drinking water down to 1 gal product to 50,000 galdrinking water. (1 gal/10,000 gal to 1 gal/50,000 gal on an activeingredient concentration basis: 1-50 ppb active ingredient.) Use ofhigher concentrations of the product are not as useful in depositcontrol or in some cases too aggressive because too much material fromsurfaces may be too quickly entrained into the bulk water deleteriouslyaffecting water quality.

In real world trials with well-designed controls and observations,RE-Ox® Deposition Control Chemical also reduced chlorine demand by16-31%, reduced THMs 66% and HAA5s 28% in municipal drinking waterdistribution systems while water quality was maintained and unsolicitedcustomer compliments were received.

By lowering chlorine demand, the DBPs created in the distribution systemcorrespondingly are reduced and help public water systems qualify for awaiver to many requirements of the Stage 2 DBP EPA regulatoryrequirements. In addition to reducing already relatively low chlorinedemand and DBPs, RE-Ox® is useful for its water softeningcharacteristics.

Ion exchange water softening is used for drinking water in areas wherecalcium carbonate, other calcium salts and iron oxide precipitationcauses deposits on surfaces known as scale. Very low concentrations ofRE-Ox® (e.g., 1-50 ppb active ingredient) applied to drinking water,reduces the need for water softening and in some cases has eveneliminated the need for water softening altogether. The reason for thisappears to be that low concentrations of RE-Ox® (far below theconcentration necessary to kill microorganisms in drinking water) havean effect on the deposit matrix which includes inorganic and organicconstituents that are subject to oxidation. In the “real world, thesescaling deposits never include only inorganic salts (such as calciumcarbonate); rather, they are always in nature a matrix of many differentcompounds some of which are organic. The organic compounds in the matrixare derived from living materials but are not necessarily living (theorganics in these deposits can be and often are, inanimate andnon-viable) and in other cases, there are in fact living organisms inthese deposits commonly referred to as scale. The organic component ofthese deposits cause them to be much more sticky and give themcharacteristics different than the deposits would be if there were noorganics present in the deposits. By conditioning the water with RE-Ox®oxidant, less scaling precipitate forms on surfaces. This effect hasbeen very useful because reducing the need for water softening savesmoney and is environmentally preferred due to the elimination orreduction of brine waste from the water softening process.

The organic compounds in deposits on drinking water system componentsare oxidized by the unique combination of oxidants in RE-Ox®. The effectof these oxidations is to disrupt the deposit matrix. Disruption of thedeposit matrix leads to gradual removal of deposit due the scouringaction of flowing water over the surface. Deposit control is beneficialbecause of its positive effect on water quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flow chart of the stages of the RE-Ox® system;

FIG. 2 shows the brine creation stage;

FIG. 3 shows brine supply stage;

FIG. 4 shows the reactor processing stage;

FIG. 5 shows waste removal stage;

FIG. 6 shows the acid supply stage;

FIG. 7 shows the output stage;

FIG. 8 shows the reactor cell;

FIG. 9 illustrates a test of pipes and valves taken from service andassembled to receive a flow of RE-Ox® treated water;

FIG. 10 shows results after RE-Ox® treatment (right side photos) showingdeposits were removed from the pipe and valve surfaces with RE-Ox® inchlorinated water;

FIG. 11 shows a diagram of a test assembly;

FIG. 12(A) is a photo inside of a PVC pipe showing the end of test pipewith deposit material reducing pipe flow area to approximately 30% ofpipe ID before RE-Ox® treatment;

FIG. 12(B) is a photo of the end of pipe 1 after 106 days, RE-Ox®treated water removed approximately 50% of deposit material;

FIG. 13 shows that an entire length of 14′ long pipe was uniformlyencrusted with tuberculation;

FIG. 14 shows that deposition was reduced by RE-Ox® treated water asshown in pipes from a test assembly after treatment;

FIG. 15 is a bar chart showing hot water Legionella bacteria count(cfu/ml) as a function of sampling period, with sampling periods 1 to 4prior to treatment with RE-Ox® , and with sampling periods 5 to 13 aftertreatment with RE-Ox®;

FIG. 16 is a bar chart showing hot water copper averages (ppm) as afunction of sampling period, with sampling periods 1 to 4 prior totreatment with RE-Ox® , and with sampling periods 5 to 13 aftertreatment with RE-Ox®;

FIG. 17 is a bar chart showing cold water copper averages (ppm) as afunction of sampling period, with sampling periods 1 to 4 prior totreatment with RE-Ox® , and with sampling periods 5 to 13 aftertreatment with RE-Ox®;

FIG. 18 is a bar chart showing hot water lead averages (ppm) as afunction of sampling period, with sampling periods 1 to 4 prior totreatment with RE-Ox® , and with sampling periods 5 to 13 aftertreatment with RE-Ox®;

FIG. 19 is a bar chart showing cold water lead averages (ppm) as afunction of sampling period, with sampling periods 1 to 4 prior totreatment with RE-Ox®, and with sampling periods 5 to 13 after treatmentwith RE-Ox®;

FIG. 20 is a bar chart showing hot water average heterotrophic bacteriacount (cfu/ml) as a function of sampling period, with sampling periods 1to 4 prior to treatment with RE-Ox® , and with sampling periods 5 to 13after treatment with RE-Ox®;

FIG. 21 is a bar chart showing cold water average heterotrophic bacteriacount (cfu/ml) as a function of sampling period, with sampling periods 1to 4 prior to treatment with RE-Ox® , and with sampling periods 5 to 13after treatment with RE-Ox®;

FIG. 22 is a table showing total chlorine residuals as a function ofsampling site for twenty-nine (29) sampling sites, with readings beforetreatment with RE-Ox® (10-month average), during a burnout period, andafter treatment with RE-Ox® (2-month average);

FIG. 23 embodies Table 1, providing TDA, ORP, and Free Available Cl₂data as a function of sampling point for chlorinated water (averages of17 samples taken from each sampling point location) before treatmentwith RE-Ox®;

FIG. 24 embodies Table 2, providing TDA, ORP, and Free Available Cl₂data as a function of sampling point for chlorinated water (averages of8 samples taken from each sampling point location) after treatment withRE-Ox®;

FIG. 25 embodies Table 3, providing average results (Cl₂, ORP, pH, TDS,and turbidity) for raw water, RE-Ox® treated water, and discharge water,respectively;

FIG. 26 embodies Table 4, providing data for treatment of three pipesections following treatment with RE-Ox®;

FIGS. 27A-27B embody Table 5 (presented in two sections), providing testdata (COND, TDS, ORP, pH, total Cl₂, free Cl₂, and total volume) forcity water, and for water treated with RE-Ox®; and

FIGS. 28A-28B embody Table 6 (presented in two sections), providing datafor various analytes for water treated with RE-Ox®.

DETAILED DESCRIPTION

RE-Ox® technology, a specially formulated cleaning solution of activatedsodium hypochlorite (NaOCl, bleach) engineered to eliminate scale andbiofilm deposits from pipe during normal operations while maintainingwater quality, has the unique ability to readily penetrate inorganicdeposits as well as organic deposits/biofilms and destroy the organicglue that holds them together. RE-Ox® is non-hazardous, neutral pH,odorless and tasteless in water, and is NSF Standard 60 registered fordrinking water. RE-Ox® technology is also used to controldeposits/solids in various industries, including food processing,agriculture, healthcare and hospitality water distribution systems.

The RE-Ox® System 10 (FIG. 1) involves the production of an activatedsodium hypochlorite that can be delivered to the customer, and does nothave to be made on site. As seen in FIG. 1, the RE-Ox® System 10involves six stages: brine creation 100, brine supply 200, reactorprocessing 300, waste removal 400, acid supply 500, and output 600.

In one embodiment, the entire process is conducted in an openenvironment temperature (˜75 deg. F, +/−40 deg). Other embodimentsinvolve the use of controlled, air-supply conditioned facilities forstages such as the reactor processing 300, waste removal 400, and acid500. Other embodiments also involve the elimination of one or more ofthese stages, the consolidation of one or more stages, and the additionof more stages.

The brine creation stage 100 involves the creation of diluted brine 120and is shown in more detail in FIG. 2. First, concentrated brine 102 iscreated in a concentrated brine tank 104. Sand 106 is placed in thebottom of the concentrated brine tank 104. Next, salt 108 is added intothe concentrated brine tank 104. Water 110 is then added from a watersupply 112.

Various grades of sand 106 can be used. The sand 106 is meant to serveas a filter, to act as a diffusing bed and to help supply uniformconcentrated brine 102. In other embodiments, the sand 106 is replacedby diffusion beds or other media. In an embodiment, the salt 108 is99.9% pure food high grade Morton brand sodium chloride (NaCl), thoughother embodiments involve the substitution of various other types,brands, and grades of salt 108. Sodium bromide, potassium chloride,potassium iodide, and calcium chloride are also contemplated.

The water supply 112 in the current embodiment is the municipal tapwater supply. Other embodiments involve the use of water 110 fromdifferent water supplies 112. Highly mineralized, low mineralized,chlorinated, and chloraminated water 110 have all been used with nonoticeable impact on the final product's performance.

The concentrated brine 102 is created by dissolving salt 108 in thewater 110. In the current embodiment, concentrated brine 102 is createdby passing water 110 through salt 108 in the concentrated brine tank104. The water 110 is pulled through a concentrated brine tank output114 and through a filter 116 by a concentrated brine pump 118. Otherembodiments involve various other techniques of dissolving salt 108 inwater 110. The salt 108 can be mixed with the water 110. The use ofconcentrated brine pump 118 can also be avoided by using gravity andvalves.

Next, the concentrated brine 102 is used to make the diluted brine 120.The pump 118 is used to add concentrated brine 102 into a diluted brinetank 122. Water 110 is added into diluted brine tank 122 so that theconductivity of the diluted brine 120 is 9-10 millisiemens as measuredby a conductivity meter. In other embodiments the targeted conductivityof the diluted brine 120 is different. For example, a conductivity of25-30 millisiemens has been used with no noticeable impact on the finalproduct's performance. Next, the diluted brine 120 exits the dilutedbrine tank 122 through the diluted brine output 124 and enters the brinesupply stage 200.

The water 110 added to make the diluted brine 120 can be the same ordifferent water supply 112 that is used to make the concentrated brine102. In other embodiments, the diluted brine 120 is produced initially,without making concentrated brine 102 first by mixing given amounts ofsalt 108 with water 110.

Brine supply stage 200 involves the supply of diluted brine 120 to thereactor processing stage 300. As seen in FIG. 3, a diluted brine pump202 is used to add the diluted brine 120 into a diluted brine holdingtank 204. A supply pump 206 pulls diluted brine 120 through a holdingtank output 208. The diluted brine 120 next passes through a screen 210,through a pressure regulator 212, and into the FEM processing stage 300.The pressure regulator 212 is used to deliver diluted brine 120 at adesired pressure and flow rate into the reactor processing stage 300.

A bypass 214 is also added to the brine supply stage 200 to help adjustthe pressure before the diluted brine 120 reaches the pressure regulator212. The bypass 214 includes a bypass entry 216 located before thepressure regulator 212, a bypass needle valve 218, and a bypass exitthat returns to the diluted brine holding tank 204. The bypass needlevalve 218 is opened or closed to decrease or increase the pressure andflow rate of the diluted brine 120 entering the pressure regulator 212.

In other embodiments, all or parts of the brine supply stage 200 areremoved. Diluted brine 120 can be added to the reactor processing stage300 directly from the brine creation stage 100. The use of the dilutedbrine holding tank 204 and diluted brine pump 202 can also beeliminated. The bypass 214 can also be eliminated. The pressure and flowrate of the diluted brine 120 entering the pressure regulator 212 andreactor processing stage 300 can be controlled in many different ways.

During the reactor processing stage 300, the diluted brine 120 iselectrolyzed in reactor cells 302 to produce activated sodiumhypochlorite 326. The reactor cells 302, also known as flow electrodemodules (FEMs), are composed of three concentric components. A currentembodiment is shown in FIG. 8. Other embodiments have used reactor cells302 purchased from the VIIIMT Institute in Moscow Russia.

The reactors cells 302 include a center anode 330. The center anode 330is titanium coated with a material consisting of iridium, rubidium,ruthenium, and tin. In one embodiment the iridium content is 48%-24%,the tin content is 40%-54%, the Ruthenium content is 8%-15%, and therubidium content is 4%-7%. In other embodiments, the center anode iscoated with pt-iridium. The material used for the center anode 330 canbe varied based on conductivity, durability, and cost considerations.Various Siemens coatings can also be used.

Surrounding the center anode 330 is a membrane 332. The membrane 332 isceramic. In one embodiment the membrane 332 is made from alumina. Inother embodiments, an alumina and zirconia blend is used for themembrane 332. Various materials can also be used for the membrane 332depending on porosity, insulative, durability, and cost considerations.

Beyond the membrane 332, and forming the exterior of the reactor cell302, is the exterior cathode 334. In the current embodiment, theexterior cathode 334 is titanium. The material used for the exteriorcathode 334 can also be varied based on conductivity, durability, andcost considerations. The length of the center anode 330 is greater thanthe exterior cathode 334 by one inch more in the current embodiment whencompared with the VIIIMT Institute reactor cell 302. The membrane 332 isalso longer than the exterior cathode 334.

An inside passage 336 is formed between the center anode 330 and themembrane 332. An outside passage 338 is formed between the membrane 332and the exterior cathode 334.

At the ends of the reactor cells 302 are inside collectors 340 andoutside collectors 342. The collectors 340 and 342 are made from Teflon®or another fluoroplastic. In other embodiments, the collectors 340 and342 are made from polyethylene w/antioxidant additives. The insidecollector 340 has a passage extending into the inside passage 336 andthe outside collector 342 has a passage extending into the outsidepassage 338. The collectors 340 and 342 have female ⅛ inch national pipetaper fittings 344. The fittings 344 can have other sizes and fittingdesigns, including hose barb fittings. The top of the inside collector340 in the current embodiment is elongated by half an inch when comparedwith the VIIIMT Institute reactor cell 302.

As seen in FIG. 4, the reactor processing stage 300 begins with a feedvalve 301, that when open supplies diluted brine 120 to a reactor supplyheader 304. The reactor supply header 304 delivers diluted brine to theoutside passage 338 of the reactor cell 302 through a tube 306, fitting344, and outside collector 342.

A power supply 308 delivers a direct electrical current (DC) to thecenter anode 330. As a result, the diluted brine 120 is electrolyzed toform chlorine gas and sodium hydroxide. These compounds then react withone another to form sodium hypochlorite.

In the current embodiment, ten groups of four reactor cells 302 areemployed, for a total of forty reactor cells 302. Each reactor cell 302receives 12 volts and 10 amps. Two of the four reactor cells 302 arewired in parallel, which are wired in series with the other two reactorscells in the group of four. FIG. 4 illustrates only two of the reactorcells 302. In other embodiments different wiring configurations areemployed, including all reactor cells 302 being in series or inparallel.

This large number of reactors cells 302 forms a reactor bank that allowsfor the production of large quantities of activated sodium hypochlorite326. With this number of reactor cells 302, pressure and flow rate ofthe diluted brine entering the reactor supply header 304 is adjusted to5-10 psi and 1-2 gal/minute flow rate using the pressure regulator 212.The number of reactor cells 302 used can be increased or decreased tomeet production needs. The pressure and flow rates supplied to thereactor bank are varied depending on the number of reactor cells 302 andthe reaction.

The power supply 308 is an Allen Bradley linear unregulated unit. Inother embodiments, a linear regulated power supply or an AC/DC/AC/DCswitching power supply can be used. Any electric power supply 308providing the needed control and power is sufficient. Multiple powersupplies 308 can also be employed. The electric power to each reactorcell 302 from the power supply 308 can also be varied as needed.

With the power supply 308 on, the diluted brine 120 passes up theoutside passage 338 and exits through a outside collector 342, throughfitting 344, into tube 306, and into the recirculation header 310. Therecirculation header 310 returns the now partially activated sodiumhypochlorite 312 to the bottom of the reactor cell 302. The partiallyactivated sodium hypochlorite 312 next passes through tube 306, into theinside collector 340, and up the inside passage 336.

In an embodiment, the amount or flow rate of partially activated sodiumhypochlorite 312 passing through the inside passage 336 is reducedcompared to the amount of diluted brine 120 that passed through theoutside passage 338. This reduction in flow rate changes the flow ofions and reduces the pH of the final activated sodium hypochlorite 326.A siphon bleed 314 has been added to achieve this difference in flowrates. Without the siphon bleed 314, the final activated sodiumhypochlorite 326 pH can be as high as 8.9.

The siphon bleed 314 removes 10-20% of the partially activated sodiumhypochlorite 312 from the recirculation header 310. The siphon bleed 314includes a siphon entrance 316 in the recirculation header 310. A siphonentrance 316 connects to a siphon needle valve 318 and to a siphon exit320. The siphon exit 320 connects to a 3-way valve 322 that directs thepartially activated sodium hypochlorite 312 to waste removal 400.

The percentage of activated sodium hypochlorite 312 siphoned off iscontrolled by adjusting the siphon needle valve 318 and a supply needlevalve 324 at the end of the reactor processing stage 300. Otherembodiments involve different methods of changing the flow rates betweenthe inside and outside passages 336 and 338. The sizes of the inside andoutside passages 336 and 338 can be altered, or a buffer tank can beadded, or a pressure regulator added.

After the partially activated sodium hypochlorite passes through insidepassage 336 it becomes the final activated sodium hypochlorite 326. Theactivated sodium hypochlorite 326 passes through the inside collector340, out fitting 344, through tube 306, and into a discharge pipe 328.Next, the solution passes through a supply valve 330, supply needlevalve 324, and to the Output Stage 600.

Production of activated sodium hypochlorite 326 is periodically stoppedfor a cleaning. Cleaning involves three cycles: 1) an initial rinsecycle, 2) an acid rinse cycle, and 3) a final rinse cycle. In thecurrent embodiment, cleaning is performed once each hour of production.In other embodiments the timing of the cleaning is varied depending oncost and the amount of build up or scale. Frequent cleaning cycles havebeen shown to improve activated sodium hypochlorite 326 quality.

During the initial rinse cycle the power supply 308 is turned off, thesupply valve 330 is closed, and a rinse out valve 332 is opened. A rinseout needle valve 334 is opened to control the amount diluted brine 120that passes through and forces a split of flow through both the siphonbleed 314 and rinse out line 336. The 3-way valve 322 directs the flowof diluted brine 120 to the waste removal stage 400 after passingthrough the reactor processing stage 300. The initial rinse cycle lastsfor 80 seconds in the current embodiment; though times can varydepending on size of the unit, flow rates, cleaning frequency, anddesired results.

After the initial rinse cycle is the acid rinse cycle. During the acidrinse cycle, the power supply 308 remains off, the supply valve 330remains closed, and the rinse out valve 332 remains open. The feed valve301, however, is closed.

Acid 502 is supplied for the acid rinse cycle from the acid supply stage500. As seen in FIG. 6, the acid supply stage 500 includes an acidsupply tank 504 that supplies acid 502 to an acid holding tank 506 usingan acid supply pump 508. A solenoid valve 510 controls the flow of acidto the waste removal stage 400. An acid rinse pump 512 and acid in valve514 are used to supply acid to the reactor processing stage 300 duringthe acid rinse cycle. In the current embodiment, the acid is 5%hydrochloric acid (HCl). The strength of the acid can be varieddepending on need.

During the acid rinse cycle, the acid in valve 514 is opened and theacid 502 is allowed to pass through the reactor processing stage 300.The 3-way valve 322 is set to direct the acid 502 back to the acidholding tank 506 to be reused. The acid rinse cycle lasts for fiveminutes. In other embodiments, the length of the acid rinse cycle variesbased on the time between cleanings, size of the system, strength of theacid, and need for cleaning.

Next, during the final rinse cycle, the acid in valve 514 is closed andthe 3-way valve 322 directs the flow to the waste removal stage 400. Thefeed valve 301 is also opened. The diluted brine 120 is again runthrough the reactor processing stage for 160 seconds and goes into thewaste removal stage 400. Now the cleaning cycle is complete and therinse out valve 332 is closed, the supply valve 330 is opened, the powersupply 308 is turned back on, and production of activated sodiumhypochlorite 326 begins again.

The waste removal stage 400 involves the receipt and removal of thewaste from the siphon bleed 314 and cleaning cycle. As seen in FIG. 5,the waste removal stage includes a waste tank that receives the waste404 from the 3-way valve 322. A pH meter 406 is used to monitor the pH.Before the waste 404 can discarded, the pH must be reduced. Solenoidvalve 510 is opened to add acid 502 from the acid supply stage 500 tothe waste 404. A mixer 406 mixes the waste and once the pH is broughtdown to 7 a waste pump 408 is used to remove it to the sewer 410.

After the supply needle valve 324, the activated sodium hypochlorite 326passes into the output stage 600. As seen in FIG. 7, the activatedsodium hypochlorite 326 passes through a flow meter 602 and a pH meter604. These meters 602 and 604 can be used to automate portions of theprocess, especially the siphon bleed 314, to obtain the desired final pHof the activated sodium hypochlorite 326. After the pH meter 604 is avent line 605 to vent hydrogen gas produced during the process. Theactivated sodium hypochlorite 326 then enters a holding tank 606.

The activated sodium hypochlorite 326 in the holding tank 606 ismonitored for quality. A pH reading of 6.5-7.5 is desired. Titration isalso conducted using a Hach digital titrator Method 8209 (Hach Co.,Loveland, Colo.) to measure the total chlorine content, with anythingabove 625 ppm being acceptable.

Next the activated sodium hypochlorite 326 is pumped to an insulatedstorage tank 608. The insulation 610 helps keep the temperatureconsistent. A large concern in supplying activated sodium hypochloriteis shelf life. Degradation is caused as chlorine gas is off gassed,lowering pH, and chlorine content. Accordingly, some companies supplythe machines to produce the solution on site. These companies havereported only a shelf life of 2 weeks. In contrast, the processdescribed herein produces an effective shelf life of 3 months or more.

Degradation of the activated sodium hypochlorite 326 is a function oftemperature and time, with rapid degradation occurring in directsunlight. Reducing the temperature improves shelf life. The solutionexiting the reactor cells 302 is approximately 100° F. Chilling thesolution immediately after exiting the reactor cells 302 improves theshelf life. Improvements can also be achieved by refrigerating thesolution in the storage tank 608. In one embodiment, a fluoroplasticsheat exchanger is used. The specific fluoroplastics utilized can beKynar® polyvinylidene fluoride (PVDF) (Arkema Inc., Philadelphia, Pa.)or Teflon® polytetrafluoroethylene (E.I. du Pont de Nemours and Company,Wilmington, Del.).

From the storage tank 608, the activated sodium hypochlorite 326 ispumped into PE totes 612 or barrels. The activated sodium hypochlorite326 is a dilute oxidizer and can be corrosive over time. The bestmaterials for handling these solutions are fluoroplastics, PVC, and PE.

The activated sodium hypochlorite 326 is now ready for thetransportation 614 to the customer 616. The customer 616 then injectsthe activated sodium hypochlorite 326 into its water lines.

The customer 616 is able to utilize the activated sodium hypochlorite326 without having onsite facilities to produce the activated sodiumhypochlorite 326. Such onsite facilities can be difficult to maintain,and the quality of the activated sodium hypochlorite 326 is difficult tomonitor. The RE-Ox® System 10 allows the customer 616 to receive theactivated sodium hypochlorite 326 directly avoiding these problems.

RE-Ox® prevents nucleation which is a key requirement for thecrystallization of minerals from solution directly on surfaces.Nucleation is the beginning of scales, films and other deposits.Existing mineral scales cannot be sustained and new scales cannot formwithout continuous nucleation.

RE-Ox® disrupts the attachment mechanisms of mineral scales and otherdeposit constituents in water systems, as no other known chemicalapproved for potable water applications has been shown to do. As aresult, systems in which the RE-Ox® treated water is used rapidlybecomes cleaner and remains cleaner.

RE-Ox® treated water eliminates scale and other deposition in the entirewater distribution system without interruption to facility operation andprevents the need for facility shut down for hazardous acid treatment orpipe removal and replacement. Deposition removal in water systems,equipment, floors, walls and drains results in cleaning environments ina unique way. Metal and plastic surfaces become exceptionally clean.They are cleaned at the microscopic as well as the visual level.

Comparison To Chloraminated Water: Chloraminated water is produced byadding ammonia to chlorinated water to produce chloramines. Thesoftening/conditioning benefits of RE-Ox® treated water are due to itbeing a scale and biofilm reducing water, whereas non treated water andchloraminated water is not. The chloraminated water is significantlydeposit forming. Also, the chlorine demand in the chloraminated portionof the distribution system creates problems maintaining a chlorineresidual and the correct ratio between ammonia and chlorine resultingin, among other issues, taste and odor problems in the water. In onetrial, the DBP testing of the company's chloraminated water (THM-52μg/l, HAA5-28 μg/l) revealed significantly higher results than theirchlorinated water (THM-16.0 μg/l, HAA5-6.9 μg/l).

By removing and preventing the formation of scales and biofilm in pipe,chlorine demand is reduced so that residuals can be maintained therebyelevating water quality.

By cleaning the distribution system with RE-Ox®, thereby reducingchlorine demand, greater residuals with less chlorine are maintained.DBPs minimizes conditioned high performance water is delivered.

EXAMPLES Example 1 Use of RE-0×0 by A Suburban Water Company

A water company tested using RE-Ox® as part of its water treatment forthe 302,000 gallons of water per day it provides to its 1400 customers.The company wanted to reduce its chlorine demand to minimize DBPs inanticipation of the new EPA Stage 2 Disinfection By-product rules, andto optimize its water quality for its customers. The company found thatafter the first four months of testing, the treatment is exceedingexpectations by reducing the chlorine demand 16-31%, reducing THMs 66%and HAA5s 28%, all while water quality was maintained and unsolicitedcustomer compliments were received.

Background: The company obtains its water from two sources; its own twowells, which are chlorinated with gaseous chlorine and chloraminatedwater purchased from a city public water supply. The distribution systemhas 65 miles of pipe ranging from 1½″ PVC to 24″ ductile iron, one39,000 gallon standpipe and a new 1.5 million gallon reservoir. The twodifferently treated waters are distributed to separate areas and do notmix with each other. The company does not secondarily treat thechloraminated water. The efforts for periodic biofilm burnoff phases areexecuted by the water wholesaler.

Flushing is labor intensive, causes interruptions in service, wasteswater and is not effective in removing the scale and biofilm depositsthat develop in water distribution systems and are chlorine demand.Pigging can remove scale deposits, but is expensive and labor intensive.Pigging requires that the system be taken out of service to be done insections and also consumes extreme quantities of water. Phosphatescondition water but do not remove deposits and are a nutrient source forbacteria.

Treatment Results (First Four Months): The chlorine demand in a waterdistribution system after RE-Ox® treatment began, compared to beforetreatment, was calculated by comparing the difference in the chlorineresiduals just after chlorination at the well houses to those out at thesampling/distribution sites. (See Tables 1, 2 ,3 as embodied in FIGS.23-25.) The number of sampling sites and location of a few of the siteswere increased during the treatment phase to better observe the resultsof the RE-Ox® treatment. The RE-Ox® cleaning process was followed fromthe well house(s) through the system as the free and total chlorinesampling results came closer and the ORP increased. Comparing all thedistribution system sites before and after yielded a 1.72 ppm averageCl₂ before and 1.63 ppm after. With an average of 1.08 ppm Cl₂ beforeRE-Ox® and 1.19 ppm during treatment between the two wells, therespective demand was 0.64 ppm compared to 0.44 ppm during the firstfour months of monitored treatment showing a 0.20 ppm (31%) reduction.If a deadend sampling point (#9) is eliminated from the statisticalanalysis of the data the reduction is 0.12 ppm (23%) (0.52 ppm before,0.40 ppm after). The chlorine demand in the deadend leg has reduced 0.30ppm (21%), from 1.46 ppm before to 1.16 after (a deadend point has moredeposits because there is less flow therefore, it will take longer forthis leg to reduce deposits with the minimum flow of treated water;RE-Ox® is poorly mixed and not much RE-Ox® reaches this point). If justthe sites that were exactly the same location as sampled beforetreatment baseline are calculated, the chlorine reduction was 0.07 ppm(16%), from 0.44 before to 0.37 after.

Water testing, as required by the state, showed that the water qualitywas maintained. The water provided by the company is sampled three timeseach month and submitted to a state laboratory for testing to ensurethat its water is safe and meets all requirements.

Disinfectant by-product tests on the chlorinated water sample taken at alocal site before RE-Ox® treatment resulted in 16.0 μg/l THM and 6.9μg/l HAA5. Tests on water sampled from the site on about 6 weeksafter/during RE-Ox® treatment revealed 5.43 μg/l THM and 4.0 μg/l HAA5.This represents a reduction of 66% in THM's and >28% reduction in HAA5.

Stage 2 Disinfectant By-Product Rule: The company receives some of itsfinished water from another source, so the EPA considers it aconsecutive system. The system is subject to the requirements of the newEPA Stage 2 Disinfection By-product Rule, which has been developed toimprove the quality of potable water and provide additional protectionfrom disinfection byproducts. Trihalomethanes (THM), haloacetic acids(HAA), chlorite, and bromate form when chlorine reacts to organic matterfound in water and in the distribution system deposits (system chlorinedemand). The Stage 2 rule will limit exposure to two groups of DBPs:trihalomethanes (TTHM) and haloacetic acids (HAM). Utilities will berequired to conduct an evaluation of their water distribution systemsknown as the Initial Distribution System Evaluation or IDSE. The purposeof the IDSE is to identify the locations with high concentrations ofDBPs, problem areas, initial disinfection regimes and operationalinadequacies that cause systems to develop DBPs. The systems will usethese locations as sampling sites for Stage 2 DBP rule compliancemonitoring. A waiver for this monitoring can be obtained underconditions that include the finding that for eight consecutive quarterswithin a specified eligibility period, no samples exceeded 0.040 mg/Lfor THMs and 0.030 mg/L for HAA5. The reduction of DBPs brought by thereduction of chorine demand from the RE-Ox® treatment, will aidcompanies with the waiver requirements.

Example 2 Can RE-Ox® be Used in a Public Water Supply

A State Department of Health was reluctant about the company in Example1 using RE-Ox® even though it is NSF Standard 60 registered andallowable in public water per state statutes, so a trial was conductedto demonstrate the applicability of the technology to treat public watersystems. In conjunction with other water utilities in the geographicarea, the company conducted a Pilot Trial in which RE-Ox® treatedchlorinated well water removed solids from scaled and tuberculated pipesand valves taken from service. The results were so noteworthy that asecond trial was performed using RE-Ox® in the chloraminated waterobtained from the water wholesaler.

The first part of the Pilot Trial represented an on-line constant flowtreatment in which scale was softened and reduced, chlorine demand wasreduced and turbidity was not adversely affected. The second partrepresented an off-line flushing treatment wherein the balance of RE-Ox®softened scale was flushed out of the system. The second trial inchloraminated water also removed scale and tuberculation deposits fromgalvanized pipe and water meters. Water samples were taken and testedthroughout both trials and showed that water quality was maintained. Thetrials showed that eliminating the deposits that create chlorine demandfacilitated chlorine residuals.

Example 3 Results of RE-Ox® on Deposit Laden Pipes Retrieved fromService

A city water department conducted a trial to verify the deposit removalcapability of RE-Ox® treated water on 2″ pipes retrieved from service.The pipe was heavily tuberculated with iron, scale and biofilm deposits.The deposit material had reduced the pipe open area to be approximately30% of total pipe inner dimension. (See Table 4 (FIG. 26), FIG. 11, andFIGS. 12(A)-(B)).

The pipe was made in 1948 and has been in service since 1950. The pipewas taken out of service and divided into 3 sections, photographed andeach was weighed after drying for one day. Pipe number 1 was soaked inundiluted RE-Ox® for 8 hours, allowed to dry one day and then weighedagain. The presoaking treatment caused 1 lb (17%) of the material torelease.

All three pipes were assembled consecutively inside a 6″ PVC pipe soRE-Ox® treated water would flow through. A simple peristaltic chemicalpump provided RE-Ox® to water diverted to test assembly dosing 1 gallonof RE-Ox® to 5000 gallons of treated water. Treated water flowed at 2gpm.

After 106 days of continuous treatment, pipes were removed and allowedto dry for one day. Visual inspection verified significant depositremoval and increase in pipe ID. Pipe weights after drying one dayrevealed 50% total matter removal for pipe number 1. This was attributedto it being pre-soaked.

The pilot test was simple to set up and to monitor on site. The markedability of RE-Ox® to eliminate tuberculation is seen as a potentialreplacement for phosphates for corrosion and deposit prevention (longterm) and as a remediation methodology to clean the utility distributionsystem over the next few years. Anticipated system remediation dosingrate would be 1/15,000

In terms of water quality, daily sampling showed elevated chlorineresiduals and lower turbidity rates.

Example 4 Results of RE-Ox® Water Treatment on Water Meters andGalvanized Pipe in Chloraminated Water

RE-Ox® treated water was used to remove deposition from tuberculatedpipes and scaled water meters. RE-Ox® treatment represented an inservice treatment of cleaning pipes in chloraminated water. Having showneffectiveness in chlorine treated water, it was thought that RE-Ox®might not be effective in chloramine treated water. However, RE-Ox®treatment caused deposits to soften and disintegrate, water quality wasmaintained, chlorine residuals were maintained, and turbidity did notoverly increase. This trial demonstrates the applicability of RE-Ox®treatment in public water systems, even when chloraminated, withoutinterruption of service to the customer.

1. Pipes and meters were retrieved from water utility distributionsystems, including:

-   -   3-34″ Water Meters    -   14′ of 1″ Galvanized Pipe

2. The pipe had uniform tuberculation throughout its length. The pipewas cut into six sections. Three sections were set aside as a controland three were assembled in series along with the meters. This assemblywas connected to a 1″ water supply line, providing chloramine treatedwater from distribution branch. RE-Ox® was added to the supply waterjust prior to entering the test assembly with a water-drivenproportional chemical pump.

3. Water supply flowed continually. Water volume was changedperiodically to approximate normal use and averaged 2 gpm.

4. RE-Ox® treatment ran for about 4 months. Water chemistry analysis wasperformed regularly on incoming city water and water leaving testpiping/meters. Samples of water leaving test assembly were takenthroughout the trial for typical water quality analysis to test forconformance to Federal and State requirements.

Results:

-   -   A. Scaling and deposits reduced (FIGS. 13, 14)    -   B. Water quality was maintained and safe to drink    -   C. Water quality met or exceeded federal and state requirements    -   D. Chlorine residuals maintained to end of system    -   E. Turbidity did not overly increase

Example 5 Water Improvement in a University Hospital

A building in a University Medical Center had a Legionella contaminationproblem. Quarterly remediation had been necessary using thermal means.Chlorine dioxide was used throughout campus, but a secondarydisinfectant was necessary at this building.

Common Objections/Concerns To Hyper-Chlorination

Hyper-chlorination is a short-term fix for Legionella remediation.Because it is not effective at biofilm and deposit removal, Legionellawill quickly re-populate. Also high levels of chlorine create acorrosive environment that destroy alloy and steel piping. The corrosivenature of hyper-chlorination could release corrosion by-products such aslead and copper. Hyper-chlorination causes disinfectant by-products(DBPs) such as haloacetic acids and trihalomethanes, which is a knowncancer carcinogen. Hyperchlorination can also increase the pH of thewaters which can lead to other corrosive properties.

Trial Description

RE-Ox® product was injected into the incoming city water line to thebuilding. The product was fed via proportional feed based on water flow.The water feeds the domestic cold and recirculating hot water systems.23 distal points were measured for environmental changes. Baselinesampling was conducted at these points for 4 weeks prior to the start ofRE-Ox® program. Sampling was conducted for another 8 weeks after thestart of the RE-Ox® treatment. The overall intent of the trial was tomeasure the effectiveness of RE-Ox® for the removal and prevention ofLegionella bacteria.

Besides the effect on the taste and odor of the water, other concernsneeded to be addressed when adding a chemical to a potable water systems(i.e. water had to be within acceptable standards):

Legionella bacteria (CDC);

Corrosivity (Langelier and Ryznar Indices);

Release of lead or copper (EPA 200.8);

Volatile organic compounds (EPA 502.2);

Trihalomethanes (EPA 502.2);

Haloacetic acids (EPA 552.2); and

Heterotrophic bacteria (EPA SM92 15).

Conclusions of the trial using Re-Ox® included:

Legionella bacteria was eliminated (see FIG. 15);

Corrosivity not a factor;

pH was not affected;

Volatile organic chemicals were not increased;

There was a slight increase in lead (see FIGS. 18-19);

Copper levels were suppressed in cold H₂O (see FIGS. 16-17);

Trihalomethanes and haloacetic acids were within relative ranges; and

Heterotrophic bacteria were suppressed (see FIGS. 20-21).

Example 6 RE-Ox® Restores Chlorine Residuals in Chloraminated Systems

Biofilm bum-out occurred during the winter months in a water system. Theobjective was to restore chlorine residuals in the area of service. Itwas recommended that RE-Ox® be added in addition to the free chlorineprovided by a Municipal Water District during the burn-out phase. Totalchlorine was limited to 5 ppm during the burn-out period to eliminatebacterial deposits that had accumulated the previous year. Thesedeposits were the precursors of higher levels of TTHM and HAA5s forDBPs. RE-Ox® was considered essential in this application for removingthe nucleation sites that harbored the bacterial deposits.

Background: The system obtains its water from two sources. In eithercase, the water received is chloraminated. To maintain residuals in itssystem, bulk sodium hypochlorite and liquid ammonium sulfate (LAS) aretypically added.

During this burnout, pH and temperature were noted as well as TDS andconductivity levels. Total chlorine residuals were taken from 29sampling points once a month. Data are provided in FIG. 22. There was atwo week bum-out period. Only RE-Ox® was added during this bum-outphase.

After burnout, the level of RE-Ox® was reduced 1/20,000 gallons to1/40,000 gallons. Total chlorine residuals were maintained at higherlevels for two months. The use of bulk sodium hypochlorite and liquidammonium sulfate (LAS) were suspended as long as Total Chlorineresiduals were maintained.

RE-Ox Treatment: The system uses approximately 6.6 gallons of RE-Ox® to225,000 gpd, which is a dosing rate of 1/40,000 gallons. Test resultswere obtained by using Hach DPD colorimetric sampling method, and wereverified through amperometric titration by the Municipal Water Districtlaboratory. The findings show that the Total Chlorine residuals obtainedby both methods were almost identical and confirmed that thedistribution system Total Chlorine residuals have been restored totargeted levels after the application of RE-Ox®. Total Chlorineresiduals remained level and elevated after the burn-out phase.

Conclusion: The application of RE-Ox® during burnout with free chlorine,in combination with a subsequent maintenance close of RE-Ox® postburnout, resulted in the complete restoration of Total Chlorineresiduals in the chloraminated distribution system.

Materials And Methods

Composition of RE-Ox®

RE-Ox® is 0.05% sodium hypochlorite in aqueous solution with a pHbetween 5 and 7.5. To produce RE-Ox®, water is activated by directcurrent in a specially designed electrolytic reactor that producesseveral oxidants. The exact composition of the resulting solution is notknown because many of the oxidants are difficult or impossible tomeasure and/or are transient. The oxidant that is most stable andeasiest to measure is sodium hypochlorite whose concentration in RE-Ox®is known.

Sodium Hypochlorite [CL] Trade Designation Product Function Max UseRE-Ox® Corrosion & Scale Control

This product can be used at or up to 17,500 mg/L.

RE-Ox® is also effective in chloraminated systems.

The residual levels of chlorine (hypochlorite ion and hypochlorousacid), chlorine dioxide, chlorate ion, chloramine and disinfectionby-products are monitored in the finished drinking water to ensurecompliance to all applicable regulations.

Cleaning the System for RE-Ox® Production

The cleaning procedure for the hourly production cycle is as follows:

80 seconds of flushing with dilute brine

300 seconds of recirculating dilute hydrochloric acid

160 seconds of flushing with dilute brine

3060 seconds of production cycle repeats.

Maintaining 7.0 pH is a delicate process, without this frequency ofcleaning, 7.0 pH could not be obtained directly off the processorswithout chemical additions. This creates a major difference in thesolution generated due to the fact that as the electrodes scale, the pHincreases, the longer the synthesis running time, the greater the changein the product produced.

Tables 1-6 are embodied in FIGS. 23-28B.

1. A method for reducing deposits in a drinking water distributionsystem, the method comprising: (a) producing liquid comprisingsupplemental oxidants by flowing salt brine solution through at leastone flow electrode module comprising a center anode, a membranesurrounding the center anode, and an outer cathode surrounding themembrane, wherein at least a portion of the solution is flowed seriallythrough an outside passage disposed between the membrane and the outercathode, and then through an inside passage disposed between the centeranode and the membrane, while electric power is applied between theanode and the cathode to electrolyze said solution; and (b) supplyingsaid liquid comprising supplemental oxidants to a drinking waterdistribution system to yield a supplemental oxidant concentration offrom 1 to 50 parts per billion in said water distribution system.
 2. Themethod of claim 1, wherein the liquid comprising supplemental oxidantshas a pH in a range of from about 6.5 to about 7.5.
 3. The method ofclaim 1, further comprising removing a portion of the solution afterflowing through the outside passage of the at least one flow electrodemodule and before flowing through the inside passage of the at least oneflow electrode module.
 4. The method of claim 1, wherein said at leastone flow electrode module comprises a first and a second flow electrodemodule arranged in series, wherein at least a portion of the solution isflowed through the first flow electrode module and then flowed throughthe second flow electrode module.
 5. The method of claim 1, wherein saidat least one flow electrode module comprises a first and a second flowelectrode module arranged in parallel, wherein a first portion of thesolution is flowed through the first flow electrode module and a secondportion of the solution is simultaneously flowed through the second flowelectrode module.
 6. The method of claim 1, wherein said at least oneflow electrode modules comprises a first group of flow electrode modulesarranged in series and a second group of flow electrode modules arrangedin series, wherein the first group of flow electrode modules and thesecond group of flow electrode modules are arranged in parallel, whereina first portion of the solution is flowed through the first group offlow electrode modules and a second portion of the solution issimultaneously flowed through the second group of flow electrodemodules.
 7. The method of claim 1, wherein said electric power issupplied to the at least one flow electrode module at a potential ofapproximately 12 V and a current of approximately 10 A.
 8. The method ofclaim 1, further comprising preparing a concentrated salt brinesolution, and diluting the concentrated salt brine solution prior tosupply of diluted salt brine solution to the at least one flow electrodemodule.
 9. The method of claim 1, further comprising supplying a primarydisinfectant to the drinking water distribution system, wherein thesupplying of said liquid comprising supplemental oxidants to thedrinking water distribution system is performed at the same facility assaid supplying of primary disinfectant to the drinking waterdistribution system.
 10. The method of claim 1, wherein the drinkingwater distribution system comprises a municipal or community drinkingwater distribution system arranged to supply potable water to waterutilizing facilities of a plurality of different customers.
 11. Themethod of claim 1, wherein the center anode comprises titanium coatedwith a coating comprising at least one of iridium, rubidium, ruthenium,and tin.
 12. The method of claim 1, wherein the membrane comprises atleast one of alumina and zirconia.
 13. The method of claim 1, whereinthe outer cathode comprises titanium.
 14. The method of claim 1, furthercomprising storing said liquid comprising supplemental oxidants in atleast one container, and transporting said at least one container to atreatment facility associated with said drinking water distributionsystem.
 15. The method of claim 1, further comprising periodicallycleaning the at least one flow electrode module, wherein said cleaningcomprises at least one acid rinse cycle and at least one subsequentrinse cycle.
 16. The method of claim 1, wherein the liquid comprisingsupplemental oxidants has a pH in a range of from about 5 to about 7.5.17. The method of claim 1, wherein said supplying of liquid comprisingsupplemental oxidants to the drinking water distribution system isperformed after water in said drinking water distribution system isdisinfected with a primary disinfectant.
 18. The method of claim 1,wherein said supplying step comprises (i) supplying said liquidcomprising supplemental oxidants to the drinking water distributionsystem during an initial treatment period at a first ratio of liquidcomprising supplemental oxidants to water to be treated, followed by(ii) supplying said liquid comprising supplemental oxidants to thedrinking water distribution system during a subsequent maintenanceperiod at a second ratio of liquid comprising supplemental oxidants towater to be treated, wherein the second ratio is substantially lowerthan the first ratio.
 19. The method of claim 18, wherein the initialtreatment period comprises at least about two weeks.
 20. The method ofclaim 18, wherein the second ratio is less than or equal to about halfof the first ratio.
 21. The method of claim 18, wherein the first ratiois in a range of from about 1 gallon of liquid comprising supplementaloxidants per 10,000 gallons of water to be treated, to about 1 gallon ofliquid comprising supplemental oxidants per 50,000 gallons of water tobe treated.
 22. The method of claim 18, wherein at least one of thefirst ratio and the second ratio is sufficient to substantially reducebacterial deposits in piping of said drinking water distribution system.23. The method of claim 18, wherein at least one of the first ratio andthe second ratio is sufficient to prevent accumulation of scalingdeposits in piping of said drinking water distribution system.